OP...don't bother, the seller will not admit to receiving them so you won't be any further ahead...or they could refuse to accept delivery and you might have to pay return postage back to you again.
A few months before Covid (2020) I bought a household item on eBay that cost 3 x times the cost of the trainers, it was supposed to heat and cool but the model that was sent was cool only, so like your DH, I opened a dispute due it being a higher cost item and as I wanted everything recorded on eBay.
Seller tried to tell me I 'bought the wrong item' but in the listing I purchased it said 'hot and cold' and the photos showed the 'hot and cold' model. The case was settled in my favour and, like you, I didn't expect to keep the item once I had a refund...but...the seller just ignored all attempts to pay for return postage and as it was heavy I wasn't prepared to pay postage so I phoned eBay and was told 'to keep the item as the seller MUST pay return postage because they made the mistake, not me.' The eBay guy also told me 'sell it on Gumtree if you don't want or need it and pocket the money.'
I waited 10 months in case the seller changed their mind but still nothing, so it went to a family who had hit a rough patch.
So tell your DH, he won't be taken to court...that's just their reaction rather than admit they made a mistake. Crazy I know but it happens. If he pays return postage, he gets further involved and goes against eBay policy.
Hope this helps?